Disease Note.

Thielaviopsis Root Rot of Corn-salad. M. E. Stanghellini, Department of Plant Pathology, University of Arizona, Tucson 85721. S. L. Rasmussen, and D. J. Barta. Department of Plant Pathology, University of Arizona, Tucson 85721, and Department of Horticulture, University of Wisconsin, Madison 53706. Plant Dis. 74:81. Accepted for publication 3 August 1989. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0081E.

In October 1988, stunted corn-salad (Valerianella locusta L.) plants showing severe root rot symptoms were obtained from a commercial greenhouse in Montour County, Pennsylvania. Thielaviopsis basicola (Berk. & Br.) Ferr. (= Chalara elegans Nag Raj & Kendrick) was consistently isolated from reddish brown lesions on roots collected throughout the greenhouse, which uses the nutrient film technique of cultivation. Species identification was based on morphological features of aleuriospores and phialoconidiophores. Pathogenicity trials, conducted under hydroponic conditions, showed that the fungus was the cause of the disease. Reddish brown lesions, bearing numerous aleuriospores, developed on roots within 5 days after inoculation at 22 C. Koch's postulates were completed. This is the first report of the fungus as a pathogen of corn-salad and is believed to be the first report of the fungus as a pathogen of any vegetable crop grown hydroponically.